Light-stable polyesters



United States Patent Claims priority, application Great Britain, June 16, 1966,

26,863/ 66 Int. Cl. C08g 17/08, 51/04, 51/56 US. Cl. 260-47 Claims ABSTRACT OF THE DISCLOSURE High molecular weight polyesters containing at percent of anatase titanium dioxide and y percent of cobalt ions, x being 1.5 to 3.0 and x/y being from 50 to 15 0.

The present invention relates to polyesters of high stability towards the degradative effect resulting from exposure to light rays.

According to the present invention we provide a high molecular weight polyester containing x percent by weight of titanium dioxide in the anatase form and y percent of cobalt ions by weight, each percentage being based on the weight of polyester, 2: being from 1.5 to 3.0 and y being such that x/y is from 50 to 150.

In the term polyester we include homopolyesters which may be prepared by the reaction of a dicarboxylic acid with a glycol, although either or both of the reactants may be in the form of a suitable derivative, copolyesters in which a minor proportion of the homopolyester re:

peating units is replaced by a second ester unit, which may or may not have a dicarboxylic acid or glycol units in common with the main repeating unit and polyester ethers wherein for each ester group thereis up to one ether group on average.

In order that they may yield valuable fibres, the polyesters for use in the process of our invention shouldbe such that at least 85 percent of their polyester units are poly(ethylene terephthalate) or are poly(ethylene-1:2-diphenoxyethane 4:4 dicarboxylate) units. Examples of suitable second carboxylic acids for preparation of copolyester are isophthalic and adipic acids. Examples of suitable glycols are those of the formula HO(CH ),,OH where n is not less than 2 and not greater than 10, and bis(hydroxymethyl) cyclohexane.

An advantage of the process of our invention is that,

by means of it polyesters may be prepared which are delustred with anatase titanium dioxide and which have a high stability towards the degradative effect of exposure to light rays, particularly to ultra-violet rays. This is of particular advantage when there is required a polyester containing a high percentage of titanium dioxide. in the anatase form as delustrant, since the presence of titanium dioxide in the anatase form in polyesters normally has an adverse effect on the light stability. A highly delustred polyester will normally contain at least 1.5% of titanium dioxide, above about 3.0% of titanium dioxide no enhanced delustring effect is observed. In particular cases, the stability of the highly delustred polyester to light rays may be higher than that of the polyester containing no titanium dioxide. Particularly advantageous results have been obtained when the ratio x/ y is from 50 to 120.

The metal may be introduced into the polyester by any suitable means. For example, in the case where the metal is an ester-interchange catalyst and the polyester is prepared by an ester-interchange process, the metal may be introduced at the beginning of the ester-interchange process and may serve as the ester-interchange catalyst with great convenience. However, where an ester-interchange catalyst is required, it is not essential that the metals of our invention should be used exclusively, or at all, as the ester-interchange catalyst; another metal may be used as ester-interchange catalyst and the metal of our invention introduced after the completion of the ester-interchange stage. The metal will normally be added in a soluble form; in cases where an insoluble or sparingly soluble form of the metal is added, the addition is preferably made early in the process of preparation of the polyester, for example at the ester-interchange stage or at the stage of reaction of dicarboxylic acid with glycol in order that the metal should have the maximum opportunity of becoming solubilized before preparation of the polyester is complete.

The titanium dioxide may be added at any suitable stage during the preparation of the polyester. Most convenient is the addition of the titanium dioxide at the end of the ester-interchange reaction in the form of a slurry in the appropriate glycol. The titanium dioxide may be in any suitable state of subdivision; that normally offered for sale as a pigment has given satisfactory results.

Other conventional additive may also be present in the polyester, for example a phosphorus compound in order to minimize thermal degradation.

Particularly high stability is obtained in the case of poly(ethylene bis(carboxyphenoxy)ethane according to the process of our invention.

In order that the process of our invention may be the more fully understood, we give hereinafter Examples 5, 6, 7, 12, 13, 14, 16, 18 and 19. Examples 1, 2, 3, 4, 8, 9, 10, 11, 15, 17 and 20 are given by way of comparison.

EXAMPLES ll-7 These examples illustrate the effect of concentration of anatase titanium dioxide as well as the nature and concentration of the stabilizing metal on the light stability of poly(ethylene terephthalate) fibres.

Poly(ethylene terephthalate) was prepared by esterinterchange of dimethyl terephthalate with excess of ethylene glycol in the presence of an ester interchange catalyst, followed by removal of the excess of glycol and polymerisation under vacuum of the resulting product in the presence of antimony trioxide as catalyst and phosphorous acid as thermal stabilizer, using conditions normally used in commercial practice. To various batches were added various amounts of ester-interchange catalyst and after the ester-interchange stage various amounts of very finely divided titanium dioxide of the anatase form were also added. The quantities of the catalysts are set out in Table 1. The polymers were melt spun and drawn under standard conditions to give 100 denier yarn comprising 48 filaments having a tenacity of 6.5 to 7 grains per denier. The yarns were wound on metal frames and exposed to direct sunlight in Florida, U.S.A., facing South at an elevation of 45. Samples of the yarns were removed after land 3 months exposure in order to measure their breaking loads. The breaking loads of the exposed fibres, expressed as a percentage of that of the unexposed fibres, are given in Table 1.

It will be clearly seen from Table 1 that the use of a salt outside the scope of this invention (e.g. calcium acetate) has no stabilizing eifect upon yarns delustred with anatase titanium dioxide and, further, that such yarns are commercially unacceptable because of their poor stability. However, the use of a salt within the scope of the invention (cobalt acetate) increases considerably the light stability of delustred yarns, particularly if the concentration of metal ions is within the preferred range. More particularly the use of the optimum cobalt acetate concentration produces a heavily delustred yarn more stable than the undelustred yarn.

TABLE 1 Percent initial breaking load retained after El. exposure to sunlight catalyst Titanium Ratio W eonccndioxide, TiOE/ Afterl After3 *lcrccntage by weight as anhydrous ester-interchange (El) catalyst on diniethy tcrephthalate, although the catalysts were added as their hydrates.

EXAMPLES 8-14 ing 2% by weight of titanium dioxide of extremely high light stability.

Fibres containing 2% unstabilized titanium dioxide of the anatase form were spun and drawn under similar conditions from poly(ethylene terephthalate) and poly (ethylene 1:2 diphenoxyethane 4:4 dicarboxylate) prepared using calcium acetate or cobalt acetate as esterinterchange catalyst. The fibres were exposed in a Weath- I r77 i 5, tion of 45 to sunlight filtered by passage through A lnch 25 55 3: 55 jg gfii? g gi g gg g i g 32:

flllick,,standard a 3 is i j an l i i breaking load retained measured periodically (Table 3). g ass exilosure 1S esmge o slmu 6 con 1 Ions It will be seen from the table that both forms of fibre under WhlCh curtain nets are normally exposed. from poly(ethylene diphenoxyethane dicam Samples were removed after 3 and 5 months In order boxylate) are more stable than the more stable form of to measure their breaking loads. These, expressed as a percentage of the unexposed fibres, are listed in Table 2. p01y ethylene terephthalate) more partlcularly h It is again clearly seen that the use of a salt outside the delustred fibres Prepared from P1y(ethy1ene 152 These examples demonstrate that the beneficial stabilization of delustred fibres to direct sunlight, described in Example 1, is also observed if the exposure is repeated 20 under glass and when salts within the scope of this invention are used.

Further samples of the yarn described in Example 1 were Wound onto metal formers and exposed at an elevascope of this invention produces delustred yarns of a phenoflethane dlcarbmfylate) a C C0fd1I1g 9 r completely unacceptable stability to sunlight for practical lllventlon have an extremely hlgh stablllty t0 aftlficlal purposes. sunhght.

TABLE 3 Percent initial breaking load retained Ester-interchange catalyst metal 67 230 396 560 726 Polyester concentration, percent" ion hrs. hrs. lns. hrs. hrs.

Example:

15 Poly(ethylene terephtlialate) 0.07 calcium acetate %H20 1 8 18.2 52.1 37.8 32.2 27. 1

16 d 0.08 cobaltous acetate 4H2O.-- 79.2 73.3 66.3 52.8 57.2

17 Poly(ethylene-1:2-diphenoxy- 0.07 calcium acetate %H2O.. 118 93.0 89.0 77.7 76.4 76.6

ethane-4:4-dicarboxylate). 18 d 0.08 eobaltous acetate 4H2O... 75 94.5 91.0 92.8 89.6 90.0

*Percentage by weight as anhydorus El. catalyst onfdimethyl ester.

The use of salts within the scope of the invention, (co- EXAMPLES 19? 20 balt acetate), considerably increased the light stability of delustred yarns. In some cases a heavily delustred yarn 50 This example illustrates the fact that the cobalt ions is obtained which is more stable than the undelustred may be added to the polyester after the completion of yarn. ester-interchange.

TABLE 2 Percent initial breaking load Ester interchange tration, Ti02 metal month's month's (E.I.) catalyst percent* percent ion exposure exposure *Percentage by weight as anhydrous El. catalyst on dimethyl tcrephthalate, although the catalysts were added as their hydrates.

Fibres were prepared from poly(ethylene 1:2-diphe- EXAMPLES 15-18 noxyethane-4:4-dicarboxylate) containing 2% by weight These examples illustrate the use of a preferred salt t of unstabilised titanium dioxide of the anatase form as the preferred concentration to give fibres from poly(ethyl- H described in Examples 17 and 18. The polyester was, ene 1:2-diphenoxyethane 4:4 dicarboxylate) contain- 0 however, prepared using 0.07% by weight of calcium TABLE 4 Percent initial breaking load TiOz/ retained Ester-interchange catalyst cobalt; Example concentration, percent* ion 385 hrs. 572 hrs.

19 0.07% calcium acetate 951320-.." 1 75 96. 8 85 20 do 95 70 1 Cobalt phosphate added after E.I.

* Percentage by Weight as anhydrous El. catalyst on dimethyl ester What we claim is:

1. A high molecular weight fiber-forming polyester of a dicarboxylic acid and a glycol wherein at least 85% of the polyester units are poly(ethylene terephthalate) or poly(ethylene-1:Z-diphenoxy ethane-4:4 dicarboxylate) units, said polyester containing x percent by Weight of titanium dioxide in anatase form and cobalt acetate or cobalt phosphate in concentrations suflicient to provide y percent of cobalt ions by weight, each percentage being based on the weight of polyester, x being from 1.5 to 3.0 and y being such that the ratio x/y is from 50 to 150.

2. A high molecular weight polyester according to glairn 1 wherein x is 2.

3. A high molecular weight polyester according to claim 1 wherein the ratio x/ y is to 120.

4. A high molecular weight polyester according to claim 1 wherein at least 85% of the polyester units are poly(ethy1ene terephthalate) units.

5. A high molecular weight polyester according to claim 1 wherein at least 85% of the polyester units are poly(ethylene-1:Z-diphenoxy ethane-4.4 dicarboxylate) units.

References Cited UNITED STATES PATENTS 2,641,592 6/1953 Hofrichter 260 2,984,647 5/1961 White et al. 26045.75 3,161,710 12/1964 Turner 260-75 3,297,650 'l/1967 Halmi 260-75 3,398,124 8/1968 Rein et a1 26075 FOREIGN PATENTS 579,462 8/ 1946 Great Britain. 610,137 10/1948 Great Britain.

OTHER REFERENCES Matiello, Protective and Decorative Coatings, title page and p. 34, vol. 11, published 1942, New York, N.Y., John Wiley & Sons.

WILLIAM H. SHORT, Primary Examiner L. P. QUAST, Assistant Examiner US. 01. X.R, zen-4o, 45.75, 75 

